It is known to provide a heating and ventilating apparatus for the cabin of a motor vehicle, comprising: a cold air admission duct: an admission and heating circuit which is connected to the cold air admission duct and which is adapted to produce a flow of cold or heated air; a distribution circuit which is connected to the admission and heating circuit and which comprises an inlet for the admission of the stream of cold or heated air together with and which are adapted to distribute, via distribution means, the stream of air into different parts of the cabin, wherein at least one of the said outlet ducts exhausts behind the windshield of the vehicle for the purpose of demisting the windshield. Such an apparatus will be referred to as an apparatus of the kind specified.
Such an apparatus is commonly used for the heating and ventilation, and sometimes for the air conditioning, of the cabin of a motor vehicle, and is arranged to deliver cold or heated air into different parts of the cabin through the various outlet ducts mentioned above. There are usually three of these outlet ducts, comprising the outlet duct which feeds the windshield demisting and de-icing vents, a duct which feeds the ventilating vents at the level of the fascia, and finally a duct which leads to a vent in the lower part of the cabin. The cold air introduced from outside the cabin, or in some cases cold air introduced through an air conditioning system, is adjusted as to its temperature by the admission and heating circuit before being released into the cabin.
Such apparatus also includes, in a known manner, a motorised blower unit which is arranged upstream of the cold air admission duct, so as to regulate the speed of the air stream that is delivered into the cabin. Most apparatuses of this type include manual, mechanical or electrical control means operated by the driver, for regulating the temperature of the air stream, its distribution between the various outlet ducts, and also the flow rate of ventilating air.
Although such apparatuses generally give satisfaction, they do have certain drawbacks. For example, when the driver
various controls so as to
at the same time, the temperature of the air
, its distribution mode, and its flow rate, that is to say he has to operate three different controls more or less at the same time. This leads to a risk that the driver may be distracted for too long from paying proper attention to his driving, to the detriment of safety; and this is aggravated by the fact that his visibility through the windshield is impaired. And then, once the misting or ice has been dispersed, the driver once again has to operate the same controls in order to restore the adjustment of the system to its previous state consistent with the required degree of comfort within the cabin. This again introduces the risk of undue distraction of the driver from his driving. The operations on the controls in order to effect demisting cannot be memorised on the various manual, mechanical or electrical controls, which means that, once the misting has been cleared, the driver has either to remember what the previous settings were, or to find them again by trial and error.